[editor : Carl T. Helmers Jr.] [publisher : Virginia Londoner (Virginia Londner), Gordon R Williamson] [art : Ellen Bingham, Wai Chiu Li, Christine Dixon, Holly Carmen LaBossiere, Deborah Porter] [cover : Robert Tinney] #Magazine
#Abstract
About the Cover: on this issue's cover, Robert Tinney has created a "fantasy on homebrewing." In the middle of a sylvan glade, we see the form of a computer being sculpted by some homebrewer. A couple of humanoid forest denizens look on with wonder, perhaps hoping to get a glimpse of our homebrewer on his return to the work place.
Building a joystick interface for your computer system adds a new physical input dimension. There are as many different ways to interface a joystick as there are applications. Steve Ciarcia discusses several widely varying ways to design Joystick Interfaces. Page 10
The idea of having a microcomputer work in a multiprogramming environment is becoming a reality. Already there are several multiprogramming systems on the market. Mark Dahmke provides an Introduction to Multiprogramming so we can understand how these systems operate. Page 20
If you enjoy playing chess against your computer, but dislike typing in the moves in abstract notation, you will be interested in a method of allowing the computer to detect moves made on a real chessboard . Jeff Teeters devised such a method and now tells us how he did it in Interface a Chessboard to Your KIM-1. Page 34
Some Musings On Hardware Design by Clayton Ellis provides readers with background information on picking integrated circuits and using them in homebrew work. Page 62
Although there are many applications where a high-speed analog-to-digital converter is necessary, many conversion applications can make do with a slower conversion. Richard C Hallgren has built A Low-Speed Analog-toDigital Converter for the Apple II which he uses as a real-time data analyzer. Page 70
When constructing electronic equipment, it is imperative that good Soldering Techniques are developed. William Trimmer presents a photo essay of good soldering practices and several examples of unwanted techniques. Page 84
William T Powers brings his discussion of The Nature of Robots to a close by applying the previously-discussed techniques and theories in a simple experiment with a human subject. Page 96
The search for the inexpensive paper-tape reader continues as Brian A Harron describes an Inexpensive, Optical Paper-Tape Reader. Page 118
James Albus considers the mechanisms of choice in his closing article about A Model of the Brain for Robot Control. Page 130
A Handy Pulser can prove to be very useful when testing a digital circuit. Bob Chrisp shares with us his version of a useful pulse generator. Page 160
In The AMSAT-GOLEM-80, Joe Kasser shows how your computer club (or any other group of experimenters) can economically build an S-100 microcomputer. The system is modular and expandable. Page 182
Performing simple control functions with your computer can be easy. Ken Barbier describes how to Add Some Control to Your Computer. Page 196
[author : Carl Helmers] #Edito
Extract : « In this issue of BYTE, we are placing a special emphasis on the homebrewing of computers: the craft of assembling the hardware and software of a system from standard components in nonstandard ways. This month's editorial provides a continuation of notes begun in July on the design and assembly of my new homebrew 6809 system. In this editorial, we complete the final details of the physical layout and power supplies of the system, as well as the overall design of the system. We shall also begin a discussion of the actual processor card. Future installments in this series on homebrew, general purpose, computer hardware will record details of the system beyond this article's goal of defining a backplane bus structure.
As noted earlier ("Editorial," June 1979 BYTE, page 6), the intent of this exercise is to develop a specialized controller node for a loosely coupled system of processors involved with musical applications. The multiple processors initially contemplated were a Pascal-oriented, large personal computer and an ALF products model AD-8 music synthesizer with its 6502 used for housekeeping. In addition to this coordinating task, the 6809 would provide a central point for the connection of keyboards, displays and other hardware required by musical applications.
But ideas change and evolve. Since the 1st installments were written, plans have become slightly more grandiose with my recent acquisition of a New England Digital "Synclavier" music synthesizer and its associated Able/60 minicomputer. [...] »
TABLE OF CONTENTS
An interface for every purpose
[author : Steve Ciarcia] #Electronic #Interface #DataAcquisition #Game
Extract : « The thought that often comes to mind when the word joystick is mentioned to a computer enthusiast is of a spacewar-type game. A photon torpedo is fired from an opponent's starship, and the thruster joystick is deftly moved to reposition the craft out of its path. All of this occurs without having to take your eyes off the screen. Eye/hand coordination is almost "instinctive." With a glance to the upper right of the video screen, the joystick is tilted to the upper-right corner of its 360° range. This moves the spacecraft toward that coordinate. Reverse thrust is accomplished by moving the joystick in the opposite direction, as though you are pulling back on the throttle of a real craft. Such is the general experience with joysticks. However, the potential use of these devices greatly exceeds that of game playing.
A joystick, for those people who are unfamiliar with one, is shown in photo 1. It is an electromechanical device with resistance outputs proportional to the X,Y displacement of a central ball and lever. [...] »
Some basic concepts
[author : Mark Dahmke] #Initiation #Programming #Book
Extract : « Multiprogramming has usually been considered out of reach of the average personal computer experimenter using a small or medium scale computer. Actually, anyone with a processor above the level of an 8008 can operate a multiprogram or multiuser system. The original purpose of multiprogramming was to allow more than 1 user to take advantage of a computer simultaneously. This increased the productivity of the machine by allowing programs to run while other programs were awaiting user input, access to a disk, etc.
This may seem to conflict with the advantages inherent in microprocessor based systems (single user systems and low cost). However, there are many instances where the ability to run more than 1 program at a time may be advantageous. Note that the statement "more than 1 program may run at a time" does not mean simultaneous execution. That is the definition of multiprocessing (more than 1 processor on the bus), not multiprogramming.
To describe multiprogramming more effectively, I shall refer to a more well-known function in computers: real-time interrupts. [...] »
Play chess with a computer as easily as with a human opponent
[author : Jeff Teeters] #Electronic #Listing #Assembly #Interface #GameBoard
Extract : « Chess is a fascinating game. Computer chess is especially fascinating because the complex analysis which determines each move is performed by a machine instead of a human. Computer chess offers an excellent way to demonstrate the power and versatility of personal computers.
Most computer chess systems are unable to "see" a chessboard. A human playing against a computer will usually set up a chessboard beside the computer, and the moves will be communicated to and from the machine through the use of a keyboard and a display in some type of abstract notation.
Keyboard entry of moves is undesirable. It is inconvenient, error prone, and inelegant. The abstract notation promotes errors and makes play difficult for people who do not know the notation system. Furthermore, errors may not be detected until many intervening moves have occurred.
An ideal chess-playing system would contain a digital television camera to observe the board and a mechanical arm to move the pieces. [...] »
Perform real-time data analysis
[author : Richard C Hallgren] #Electronic #Algorithm #Listing #Assembly #BASIC
Extract : « The development of microprocessor-based computer systems has progressed to the point where it is now practical to utilize these systems in a scientific or laboratory application. To be useful in a scientific application the computer must have the capability of converting analog signals to digital signals. Very few home computers have this capability. Certainly it is a straightforward task to design an analog-to-digital converter (ADC), but the real problem lies in connecting the converter to the computer.
The Apple II computer, with 8 peripheral-board connectors on the mother board, makes the job of designing and implementing special interfaces (such as the ADC) relatively easy. The peripheral-board connectors give the hardware designer access to all address, data, and control lines. In addition all control, address, and data lines have been buffered, and certain address bits have been decoded to give a device select (DS) signal. What this means is that when a specific range of address locations is accessed, the DS line will give a low output signal. Since the peripheral-board connectors are on the main computer board, the finished interface board will be inside the computer and will be able to use the computer's power supply. Because of these characteristics, turning the Apple II into a realtime data analyzer becomes a matter of designing an analog-to-digital converter circuit, and control logic to meet the need of the application. [...] »
A simple, human experiment
[author : William T Powers] #HowItWorks #Listing #BASIC #Assembly #Robotics
Extract : « [...] The experiment to be described in this article is so simple that it may look elementary. Nevertheless, it is the starting point for a new approach to exploring the organization of human beings. Most new ideas start by looking like old ones, but with a twist that leads in unexpected directions. If you are familiar with tracking experiments, do not be too quick to decide what this is all about. [...] »
A manual paper-tape reader with no moving parts
[author : Brian A Harron] #Electronic #Listing #Assembly #DataAcquisition
Extract : « This was the terrible equation I had to contend with every time I wanted to play my favorite game program. It would take me 30 minutes to load the 8 K BASIC paper tape. But not any more!
The solution is a 400 character per second paper-tape reader that can interface to any 8-bit input port of almost any microprocessor. It uses only 2 integrated circuits and costs approximately $15.
I had always wanted something faster than my old reliable Teletype, but I never seemed to have the $40 to $100 that was needed to buy one of the many available kits. I also wondered why most of these kits required so many integrated circuits to accomplish the simple task of latching 8 bits of data. There are 7 bits (sometimes 8 bits) of parallel papertape data spaced at regular intervals, and a sprocket hole for strobing, included at no extra cost. Why not design a self-strobing, 8-bit data latch using an inexpensive large scale integration (LSI) transistor-transistor logic (TTL) integrated circuit, the INTEL 82127. [...] »
Decision-making procedures
[author : James Albus] #ArtificialIntelligence #Book
Extract : « The essence of a hierarchy is that control is top-down. The ultimate choices are made at the top, and the goals selected at this level are decomposed into action as they filter down through the various levels of the hierarchy. For the purposes of our discussion, we will define the highest level H function in the behavior-generating hierarchy of the human brain as the will.
For centuries philosophers and theologians have debated the nature of the will, particularly the question of whether humans have "free" will (ie: the freedom to choose goals) or whether all choice is merely a reflexive or predestined response to the environment. We shall not presume to deal with this question here, other than to suggest what types of inputs are available to this highest level goal selection module. [...] »
Simple design techniques
[author : Clayton Ellis] #Electronic #Method
Extract : « The purpose of this article is to acquaint the reader with some of the more interesting types of transistor-transistor logic (TTL) integrated circuits, the ease with which logic design can be accomplished, and to offer a few design considerations and troubleshooting hints to stimulate the homebrew use of digital logic.
Taking the topics in the above order, we start with a look at some of the more complex types of TTL chips in the "74xx" series. (We will ignore simple gates for the most part.) An example is the 7442. This integrated circuit is a binary coded decimal (sometimes called BCD) to decimal decoder. What this means is that the circuit will decode 1 line out of 10 based on a 4 bit binary code. [...] »
A picture essay
[author : William Trimmer] #Electronic #Method
Extract : « Anyone who can get 3 objects into the same vicinity can solder. Doing a professional job, however, requires some care and practice. This article draws on my experience in teaching electronics and a fine pamphlet prepared by NASA entitled "Soldering Electrical Connections, A Handbook" (United States Printing Office, NASA SP-5002). Good soldering techniques can save time, components and frustration. [...] »
A simple, circuit-debugging tool
[author : Bob Chrisp] #Electronic #Diagnostic
Extract : « Most of us at one time or another have had the need for a TTL (transistor-transistor logic) pulser source for troubleshooting or circuit design. Since most of us are not affluent enough to afford sophisticated test equipment we will usually kludge a TTL oscillator or pulser when the need arises. However, the next time we need our handy little circuit we end up searching our goody box only to find that we have used the parts in another piece of equipment.
What I have tried to put together is an inexpensive oscillator that hopefully will stay in 1 piece and be ready when needed. In an effort to keep it simple and inexpensive I have left out some of the niceties that are found in your more expensive commercial test gear: variable pulse level, variable offset, rise and fall time control, double pulses, etc. [...] »
A modular and inexpensive S-100 computer system
[author : Joe Kasser] #Review #Computer
Extract : « The AMSAT-GOLEM-80 Microcomputer Project provides a means for a group or club to put together an S-100 bus microcomputer in a relatively inexpensive manner. It is a modular system of hardware and software that can be built as a standalone system or superimposed on an existing S-100 machine. It is designed to be expandable and affordable. Many people who belong to microcomputer clubs, or who are learning about microprocessors, would like to own a microcomputer. However, they may not want to make the initial investment of $500 to $1500 for the basic hardware. The AMSAT- GOLEM-80 is designed to be built in stages, as finances allow. Each stage of the AMSAT-GOLEM-80 is functionally complete and can verify the performance of the next stage. It is capable of incorporating any S-100 card, contains a powerful debugging software package (AMS-80 version 5.7), and the I/O (input/output) interface handlers for your system. It is designed to be flexible and easily customized to fit your requirements. This is recommended as a group project for 3 reasons: 1) to take advantage of bulk discounts in the purchase of hardware; 2) knowledgeable individuals are available to help others; and 3) test equipment can be shared. [...] »
Let your computer influence the outside world
[author : Ken Barbier] #Electronic #Listing #Assembly #Interface
Extract : « A virtually limitless number of devices can be controlled through a single output port using time multi- plexing techniques. A series of 8-bit bytes is fetched from a control buffer in memory, and output through a single port. On the receiving end, bus buffers present the data to all the devices in parallel, but unique strobes are supplied to each device in turn, so that it can latch its own data word.
This technique is particularly useful if the devices are to be located some distance from the computer.
The hardware shown in figure 1 has been used to control devices over 50 feet from the computer without exotic line drivers and receivers. Since remote addresses for each device are generated by the hardware, only 8 data lines and 1 strobe line are required. For maximum noise immunity, shielded twisted pair cable should be used. [...] »
#Association
#Book
Extract : « Microcomputer-Based Design by John B Peatman McGraw-Hill Book Co, New York 1977 540 pages hardcover $26.95 [...]
Computer Systems Performance Evaluation by Domenic Ferrari Prentice-Hall Inc New Jersey $23.95 [...]
The Little Book of BASIC Style, How to Write a Program You Can Read John M Nevison Addison-Wesley Reading MA 1978 $5.95, paperback
TRS-80 Microcomputer Technical Reference Handbook Published by Tandy Corporation 1979 8.5 by 11 inches, 108 pages Radio Shack catalog number 26-2103 $9.95 »